The invention generally relates to weights for weighing equipment employed in laboratories or for use in classrooms for teaching mass measurement as part of weighing exercises mathematics or science curricula. More particularly, this invention relates to inexpensive, optionally color coded weights made from plastic-encased high mass round rod that resist undesired rolling about or ingestion by children and can be stacked in engaged, end-to-end relation.
Conventional, hexagonal, all-metal weights are cut from hexagon-shaped metal rod and stamped with appropriate weight markings. Such weights typically lack any matching recessed or protruding end portions for engaged or nested stacking in end-to-end relation with other such weights. Hence, if it is desired to arrange conventional weights in stacks for storage or to combine masses for use in weighing exercises, such conventional, flat all-metal weights tend to slide off one another.
In addition, the hexagon-shaped steel rod material from which such conventional weights are cut tends to cost considerably more than comparable round steel rod material. Also, because the hexagon-shaped steel rod used in the conventional weights is exposed to the environment, the exterior of the weights is ordinarily plated, which further increases manufacturing costs. Furthermore, even plated weights are vulnerable to corrosion when scratched or subjected to extended exposure in corrosive laboratory conditions.
Producing such conventional all-metal hexagon weights involves multiple expensive manufacturing steps. These steps include sawing, deburring, plating, and stamping of the mass designation on the face of the finished weight. Stamping of the mass designation typically requires an additional punch press operation or a manual hammer and punch operation.
Conventional all metal hexagon-shaped weights are typically only 1.125xe2x80x3 or less across their widest points. Objects of this size are deemed a safety hazard for children, since they fit within the 1.25xe2x80x3 diameter testing tube used as the standard for determining whether an object presents an unsafe choking risk for children.
In addition, such conventional unplated, all-metal hexagon-shaped metal weights can have pointed or sharp edges which can injure the user or damage expensive weighing equipment with which they are used.
Thus, it is an object of the present invention to provide safer weights that are encased by an outer cushioning shell of material such as plastic, and that are free of pointed or sharp edges.
It is another object of the present invention to use round steel rod as the internal weight component in weights having an external hexagonal configuration that resists undesirable rolling about.
Another object of the invention is to provide weights that can be stacked in engaged, end-to-end fashion.
It is another object of the invention to encase rod in a protective cushioning outer shell that seals the internal steel rod from moisture or corrosive agents, without the need for plating the steel component.
It is another object of the invention to provide weights having an out shell in which the mass designation is provided when the shell is formed.
It is a still further object of the invention to provide rod-encased weights in which the outer shell of encasing material increases the diameter of the weights to minimize choking hazards.
It is yet another object of the invention to provide an outer shell that encases the internal metal rod to cushion the weight, if dropped.
Yet another object of the invention is to provide a weight with an outer shell having rounded edges that are not only safer to use than prior weights but are also more aesthetically pleasing.
It is yet another object of the invention to provide weights that are color-coded to designate their mass.
It is still another object of the invention to provide weights that are easier and more cost-effective to manufacture.
These and other such objects of the invention will become apparent in the present specification, claims and drawings.
The weights of the present invention each comprise an internal generally rod-shaped member having a length and first and second opposite ends, with an outer shell substantially encasing at least a portion of the exterior of the rod-shaped member along the length of the rod-shaped member. The rod-shaped member will be made of high mass material such as steel rod. The shell preferably will be made of plastic or of an elastomeric material and will completely encase the ends and length of the rod-shaped member, so as to seal it off from environmental conditions.
The shell may comprise at least one end portion proximate at least one of the opposite ends of the rod-shaped member covering at least a portion of the end of the rod-shaped member. The shell can be configured, for example, with a hexagonal cross-section, to impede rolling. One shell opposite end portion can be configured for engaging the opposite end portion of another of the weights for stacking of two or more of the weights in an end-to-end arrangement. The shell preferably will be configured so that all of its edges are substantially rounded.
The shell may also be molded to provide a mass designation formed thereon to indicate the mass of the weight. The shell can also be color-coded either concurrently or alternatively to the molded mass designation to indicate the mass of the weight. At its narrowest point (the transverse cross sectional width), the weight preferably will be greater than 1.25xe2x80x3 across.
The invention further comprises the method of making inexpensive, optimally color coded weights made from plastic-encased high mass round rod that resist undesired rolling about or ingestion by children and can be stacked in engaged, end-to-end relation by: cutting a high mass rod material having opposite ends and a length to a desired length corresponding to the mass desired in the final encased weight; molding a shell material having a body, an interior region and at least one end portion to substantially cover at least a portion of the length and at least one end of the rod; inserting the rod material into the interior region of the shell; forming a first engagement region in the end portion of the shell material; and, configuring the first engagement region of the shell for engaging a second engagement region on another weight to facilitate stacking of two weights in an end-to-end arrangement.